478 research outputs found

    Approaches to Daily Monitoring of the SARS-CoV-2 Outbreak in Northern Italy

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    Italy was the first European country affected by the Sars-Cov-2 pandemic, with the first autochthonous case identified on Feb 21st. Specific control measures restricting social contacts were introduced by the Italian government starting from the beginning of March. In the current study we analyzed public data from the four most affected Italian regions. We (i) estimated the time-varying reproduction number (Rt), the average number of secondary cases that each infected individual would infect at time t, to monitor the positive impact of restriction measures; (ii) applied the generalized logistic and the modified Richards models to describe the epidemic pattern and obtain short-term forecasts. We observed a monotonic decrease of Rt over time in all regions, and the peak of incident cases ~2 weeks after the implementation of the first strict containment measures. Our results show that phenomenological approaches may be useful to monitor the epidemic growth in its initial phases and suggest that costly and disruptive public health controls might have had a positive impact in limiting the Sars-Cov-2 spread in Northern Italy

    Firm Heterogeneity and the Aggregate Labour Share

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    Using a static model of firm behaviour with imperfect competition on the product and labour markets, we quantify the effect of firm heterogeneity in total factor productivity, product and labour market power, wages and output prices on the aggregate labour share. In particular, we suggest a new decomposition of the aggregate labour share in terms of the first moments of the joint distribution of these variables across firms, providing a bridge between the micro and the macro approach to functional distribution. We provide an application of our method to the UK manufacturing sector, using firm-level data for the period 1998-2014. The analysis confirms that heterogeneity matters: in an economy populated only by representative firms, the labour share would be 10 percentage points lower. However, and contrary to a common narrative focussing on increasing disparities between firms, the observed decline in the aggregate labour share over the period is driven entirely by the decline in the labour share of the representative firm, mostly due to an increasing disconnect between average productivity and real wages. Changes in the dispersion of firm-level variables have contributed to slightly contain this decline

    Firm heterogeneity and the aggregate labour share

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    We propose a model-based decomposition method for the aggregate labour share in terms of the first moments of the joint distribution of total factor productivity, market power, wages and prices, and apply it to UK manufacturing using firm-level data for 1998?2014. Contrary to a narrative focussing on increasing disparities between firms, the observed decline in the aggregate labour share over the period is driven entirely by the decline in the labour share of the representative firm, mostly due to an increasing disconnect between average productivity and real wages. Changes in the dispersion of firm-level variables have contributed to slightly contain this decline

    Applied causal inference methods for sequential mediators

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    BACKGROUND: Mediation analysis aims at estimating to what extent the effect of an exposure on an outcome is explained by a set of mediators on the causal pathway between the exposure and the outcome. The total effect of the exposure on the outcome can be decomposed into an indirect effect, i.e. the effect explained by the mediators jointly, and a direct effect, i.e. the effect unexplained by the mediators. However finer decompositions are possible in presence of independent or sequential mediators. METHODS: We review four statistical methods to analyse multiple sequential mediators, the inverse odds ratio weighting approach, the inverse probability weighting approach, the imputation approach and the extended imputation approach. These approaches are compared and implemented using a case-study with the aim to investigate the mediating role of adverse reproductive outcomes and infant respiratory infections in the effect of maternal pregnancy mental health on infant wheezing in the Ninfea birth cohort. RESULTS: Using the inverse odds ratio weighting approach, the direct effect of maternal depression or anxiety in pregnancy is equal to a 59% (95% CI: 27%,94%) increased prevalence of infant wheezing and the mediated effect through adverse reproductive outcomes is equal to a 3% (95% CI: -6%,12%) increased prevalence of infant wheezing. When including infant lower respiratory infections in the mediation pathway, the direct effect decreases to 57% (95% CI: 25%,92%) and the indirect effect increases to 5% (95% CI: -5%,15%). The estimates of the effects obtained using the weighting and the imputation approaches are similar. The extended imputation approach suggests that the small joint indirect effect through adverse reproductive outcomes and lower respiratory infections is due entirely to the contribution of infant lower respiratory infections, and not to an increased prevalence of adverse reproductive outcomes. CONCLUSIONS: The four methods revealed similar results of small mediating role of adverse reproductive outcomes and early respiratory tract infections in the effect of maternal pregnancy mental health on infant wheezing. The choice of the method depends on what is the effect of main interest, the type of the variables involved in the analysis (binary, categorical, count or continuous) and the confidence in specifying the models for the exposure, the mediators and the outcome. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12874-022-01764-w
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